Wednesday, December 31, 2014

DMVPN - phase three - EIGRP

Today I’m going to test a phase 3 with EIGRP. To present all
differences, pros, cons I have changed LAN’s IP addresses ( I strongly
recommend to read my previous posts about different variances of DMVPN) :

Before I start configuring the phase 3 I would like to show some
limitations of the phase 2. As you know for phase 2 we can’t summarize
what means every spoke needs to keep all spoke routers in its routing
table to be able to establish spoke-to-spoke communication.

Let’s imagine now the routing table in a huge network with thousand
of spoke routers. If we have middle or high models as a spoke, it
shouldn’t be a problem, but in real word, in most branches, you can find
low models and for them managing so big routing table can be the
problem.

As you see above, once I generate some traffic, I can see dynamic (temporary) tunnels.
By the routing and cef tables the traffic to 100.22.22.22 should be
sent via the hub (10.10.10.1). Only the NHRP table tells you how the
traffic will be sent:

Above output shows I can send traffic to r3 using spoke-to-spoke
communication. The main pros of the phase 3 is the ability of using
‘auto-summary’ for eigrp and communication with R2 directly, what was
impossible with the phase 2.